Trevor Phillips, the chairman of the troubled Equality and Human Rights Commission, today breaks his silence following strong criticism of his leadership and admits there were "serious managerial oversights" in setting up the controversial watchdog and "painful lessons" learned.

In the wake of calls for him to step down and following a number of high-level resignations, Phillips says he "deeply" regrets the departure of key people, but pledges the commission will fight on to "propel equality from the margins to the mainstream".

Writing in the Guardian, he hits back at claims of conflict between his £110,000-a-year part-time role and his private race consultancy work, though admits he may have been "naive" for failing to see how it could be "made to appear improper by a hostile media".

His comments are his first in public following a febrile summer for the EHRC which saw him branded an "ecocentric", accused of "poor leadership" and charged with alienating commissioners by failing to consult before making questionable on-the-hoof remarks.

The former head of the Commission for Racial Equality, he was appointed chair of the £70m a year super-quango when it was launched two years ago to bring together equality bodies for gender, race and disability discrimination, as well as sexuality, age, religion and human rights.

Critics said it was impossible to reconcile so many uncompromising interest groups, with the equality minister Harriet Harman recently admitting everything had been put "into one melting pot".

Today Phillips, who describes himself as an "old school equality warrior", writes: "Much ink has been spilt on our internal organisation.

"As non-executive chair I do not run the commission's operations. I do accept that there were some serious managerial oversights during our set-up phase. But against the background of a complex (and broadly successful) merger of fiercely independent organisations with different cultures and financial systems, some of the criticisms of our executive team seem grossly unfair."

He adds that the commission's troubles had been "creatively amplified" by some commentators. Four of 16 non-executive commissioners had stood down prematurely "not seven, as widely implied".

Of the "dark innuendo" about his non-commission activities, he says: "For the record, it is simply not true that I advised Channel 4 about the Big Brother debacle. I did produce a research report for the whole TV industry about the emerging 'superdiversity' of TV audiences."

Most part-time quango chairs undertook similar professional work in their own time, says the former television executive and presenter.

"Perhaps I was naive not to see how easily this could be made to appear improper by a hostile media; a self-inflicted wound I won't make again," he says.

Ben Summerskill, chief executive of the gay rights charity, Stonewall, and the fourth commissioner to resign during one week in July, called for Phillips to go, claiming his staying would do "more harm than good".

The rash of resignations followed Phillip's re-appointment as chair by Harman, when there had been intense speculation he would be replaced.

His public remarks that the police were no longer institutionally racist, his U-turn on multiculturalism and claims it could lead Britain to "sleepwalk towards segregation", and his pre-election musing that Barack Obama as president might "postpone the arrival of a post-racial America" have all caused controversy.